Heating device



Feb. 19, 1957 M. NATHANSON HEATING DEVICE 2 Sheets-Sheet l Filed May 13, 1954 ATTORNEYS Feb. 19, 1957 M NATHANSON 2,782,289

HEATING DEVICE Filed May 13, 1954 2 sheets-sheet 2 INVNTOR Ma 1 Na knSan BywwM/faw y ATTORNEYS I-EATING DEVICE Max Nathanson, Montreal, Quebec, Canada Application May 13, 1954, Serial No. 429,619

11 Claims. (Cl. 2159-19) This invention relates to an electrical heating unit and to methods for forming such units.

There are on the market today many electrical heaters having wire resistance elements. However, these elements are expensive to manufacture, and are frequently fragile and easily broken by vibration or by the shock of normal handling. In the usual constructions, the wire resistance element is xed onto, and strung Vbetween a group of non-conducting posts or brackets. Such heating units have their fragile heating elements exposed and are easily damaged or ruined by shocks or blows which cause a failure in the wire element.

It is therefore an object of this invention to provide a new and improved electrical heating unit having the wire resistance elements shielded and protected from physical and chemical reactions.

It is a further object of this invention to provide an electrical heating element which may be easily and economically assembled and which will form a permanent and integral part of the entire heating unit.

These and other objects of the invention will be fully understood from the following detailed description of a typical preferred form and application of the ivention, and the appended claims.

The invention may be best understood with reference to the accompanying drawings in which:

Figure l is a plan View of a heating panel;

Figure 2 is a fragmentary View, taken in perspective, illustrating a detail of construction;

Figure 3 is a fragmentary elevational view, taken in section, illustrating a detail of construction;

Figure 4 is a fragmentary elevational View, taken in section, illustrating a detail of construction;

Figure 5 is an elevational view of the panel shown in Figure l; n

Figure 6 is a plan view of a modification of the heating panel;

Figure 7 is a plan view of another modification of the heating panel;

Figure 8 is a plan view of still another modification of the heating panel;

Figure 9 is a plan view of a further modification of the heating panel; I

Figure l is a plan view of a flexible sheet particularly adapted for use as a base sheet;

Figure 11 is an elevational View` of a heating unit formed from a flexible heating panel;

Figure l2 is a section taken along lines 12--12 of Figure ll;

Figure 13 is an elevational View of a modification of the heating unit shown in Figure 11;

Figure 14 is an elevational view of a high temperature heating panel;

Figure l is a plan view of the heating panel shown in Figure 14;

Figure 16 is a schematic diagram of a circuit in accordance with this invention; and

Figure 17 is a schematic diagram of a circuit in accordance with this invention.

In Figure l there is shown a general purpose electrical resistance element which is simple, accurate, and suitable for operation in a wide range of temperatures and which may be manufactured much more economically than many heating elements being currently used. Base panel 26 is a sheet of glass-paper or other suitable material which may be plastic, ordinary paper, organic or inorganic cloth. Potential leads 22, extending longitudinally of the panel substantially the full length thereof, may be sheet copper, aluminum or other metallic or conductive material, and are cemented, bonded, or stapled tothe base sheet 20. Disposed between the bus lines, are a plurality, for example, four, heating sections 24, each of which is electrically connected in a parallel circuit with the bus lines.

Referring more particularly to Figures 2, 3 and 4, the heating sections 24 may be formed of solid or stranded wire 26, which is disposed upon and extends along one side of base sheet 20, and is fixed thereto by stitching,

stapling or sewing the element through the sheet. While the stitching may be atrandom, as relatively few stitches are necessary to securely iix'the isheet to the base, such an etect is most efficiently attained by the use of a special sewing machine, with which thestitches are made periodically at substantially similar intervals. A non-conducting filament or thread 2e -is disposed upon and extends along the second side of the base sheet 2i) in substantial alignment with the line or pattern defined by the wire element 26. As best shown in Figures 3 and 4, the individual stitches taken with the wire element 26 through the base sheet 20 may be arranged to encircle or loop Varound lament 2S. Thus the filament acts as an underthread or bobbin thread, the arrangement being such that 26 and 28 are engaged to form a lock stitch. The resistance element 26 may be formed of any of a variety of suitable metals such as copper, tungsten, aluminum, aluminum nichrome or nickel alloy, although as will be discussed hereinafter, the use of low temperature-resistance coeicient material will be preferable in certain applications. The underthread must be of a non-conducting material and it has been f ound that glass or quartz fibers are quite suitable. It may be desirable to coat the wire with an insulating material so that the current will not short circuit the loops of the stitches at 30 (Fig. 4). v

Referring more particularly to Figure 5 which illustrates the cross-section of the composite structure of the panel shown in Figure l, it is seen that the base sheet 20 carrying the bus lines 22 and the heating sections 24, composed of wire elements 26, may be provided with a cover sheet 31 on the first side of the base sheet, or with a plurality of cover sheets, 31 or 29, as well as with a cover sheet 32 disposed on the second side of the base sheet. The composite unit may also be provided with a sheet of heat retlecting material 34, such as aluminum foil, which will direct the generated heat away from the unit on the rst side of the base sheet 20. The composite structure may be made up of any selected arrangement or choice of the sheets discussed above. The superposed sheets are joined by stitching, or by bonding the various sheets together. The cover sheets may be of any iiexible non-conductive material such as glass-paper, glass cloth, ordinary paper, asbestos cloth, or other organic or inorganic insulating materials. If the'resistance element 26 has a low `operating temperature, ordinaiy paper may be used.

An eifective method of bonding consists of dipping the entire assembly of superposed sheets into a solution of silicone varnish or any other suitable high temperature bonding and insulating varnish or plastic solution' Patented Feb.` 19, '1957,'

. and .then baking the composite assembly. For a particularly strong bond, it may be desirable to eiect several dips and bakes. This bonding will not only adhesively hold the various sheets together, but will also serve to strengthen the arrangement of the heating elements 26 and will bind them ina tight relationship to the base sheet 20 and the adjacent cover'sheet 31.Y

In Figure 6 there is illustrated a modification of the invention, in which a heater having a flexible'non-com ducting base sheet 20, carrying bus line 22 lextending longitudinally substantially through the length of the panel, Vcarries the wire resistance element 36 disposed entirely on one side of the base sheet. Disposed on one side of the base sheet are a series of strips of pressure sensitive tape 38, one face of which adhesively grips the surface of the base sheet 20 while the other face adhesively engages the resistance element 36. The pressure sensitive tape serves to securely hold the lengths of the wire resistance elements 36 in their proper relative positions vwhile the selected cover sheets, for example, 29, 31, and 32, are disposed on the base Vsheet and when the composite structure is being provided with its heat reflecting sheet 34, if such is desired. When the final composite structure is fixed together into an integral body, as for example, by dipping into a resinous material, the curing of the adhesive mass about the wire elements, and between the various sheets, serves to permanently hold the wire elements in their preselected positions, as discussed hereinabove.

In Figures 7 and 8, there is illustrated another modification of the invention in which the base sheet 20, carrying bus line 22 extending longitudinally substantially through the length of the panel, carries wire resistance elements 40 disposed entirely from its rst side. This element is fixedV to the base sheet by driving staples about the wire and through the base sheet, with the'ends of the staples closed on the back or second side of this sheet. The staples hold the various portions of Ythe wire element 36 in their preselected positions, while the base sheet, the wire element, and the various selected cover and heat reflecting sheets are attached, sewn, or bonded together to form a compositel structure. lf this composite structure is bonded by the alternately dipping and baking method mentioned above in the discussion in the use of silicone varnishes, the bonding agent or material will also serve to adhesively xthe various portions of the wire resistance element in their preselected positions and will enhancethe strength and durability of the various elements composing the entirestructure.

InfFigure 8 there is illustrated a modification of the invention in which a flexible non-conductive base sheet 20, which may be formed of any of the materials discussed above, is provided with a longitudinally extending bus line,2 2 which conducts the electrical charge to a heating sectionvformed on a first side of the base sheet 20. Thisheating sectionhas thewire resistance element 42disposed entirely on one side of the base sheet20 and threaded through a ilexible glass tube 44 which is iixed to the kbase sheet by any suitablemeans. In the assembly illustrated in Figure 8, the tubing is secured to the base sheet V20`by a stapling arrangement but it is entirely within the contemplation 'of this invention'to attach the tubingby any other suitable method such as sewing, stitching, or cementing. Such'aheating panel may be provided with various cover sheets and/or heat rellecting sheets discussed hereinabove `and the en-l tire composite assembly may be joined into a unitary structure lby stitching, stapling or by bonding thevarious layers with a resinous material, as, for example, ,by dipping the composite` assembly of superposedllayers into a bathofa silicone varnish or any other high-temperature bonding r insulating varnish for plastic v4solution and by then curing the varnish by either normal or induced drying.

In Figure 9 there is illustrated another modification of the invention in which the first surface of the flexible base sheet 20 carries strips of pressure sensitive tape 46 which has insulating beads 48 sewn thereon. These beads are apertured or pierced and are disposed with their bore lying in a plane parallel to the surface of the base sheet 20. The usual wire resistance elements 50, discussed hereinabove, are threaded through the apertures of the beads and drawn taut, and thus do not actually contact the surface of the base sheet 20. This heater may be provided with one or more flexible non-conducting cover sheets and/or a heat reflecting back sheet, as discussed hereinabove. The entire composite assembly may be joined into a unitary structure by stitching, stapling, or by adhesively bonding with a resinous material, as, for example, by dipping the composite assembly of superposed layers into a silicone varnish or other high temperature varnish or plastic solution and by then curing, either by natural or induced drying.

In Figure 10 there is illustrated a typical base sheet 20 having lines 52 printed thereon with a permanent or semi-permanent ink. These guide lines are extremely helpful in installing, or ailixing the wiring to the ex ible base sheet when any of the hereinabove discussed methods are utilized. For example, when the wire resistance element is being sewn or being stapled to the flexible sheet 20 the guide lines aid the operator of the stapling or sewing machine, making the practice of the process more expeditious and hence more economical.

In Figures l1 and 12, there is illustrated an exemplary utilization of heating panels composed of a base layer of flexible non-conducting material having one or more -cover sheets, and heat reflecting sheets, aixed or bonded thereto. Here a heating panel formed in accordance withthis invention is impregnated with a plastic material, such as a resinous plastic, and polymerized in a suitable mold to ythe U-shaped configuration best illustrated in Figure 12. The wire resistance elements may be so disposed that they extend along one-half of the composite structure 5,4, or, they may, inV accordance with this invention, extend along the entire area ofthe composite structure sothat the heater will effectively radiate considerable quantities of heat from lboth sides or legs of the Ll-shaped structure. The end closures 56, which maybe formed of metal or molded from a suitable plastic material, are lxed to the composite panel 54, and provide a suitable support and framing for the heating fixture. The wires of connecting cord 58 may be electrically engaged with the heating element 24 of the heating panel in the usual manner such as by a soldered, riveted, or other connection.

InFigure 13.ther e is illustrated a slight modification of the apparatus illustrated in Figures 1l and 1,2. It will be seen that it is within the contemplation of this invention to vary the pattern or placement of the wire resistance elements within the composite panel 54. Itis purely a matter of choice whether the elements are selectively to` extend vertically or horizontally or in any other direction or with any other'given shape. It will also be seen that the exact proportion of the structure defined by the U-shape element 54 may vary according to the desires or needs of the manufacturer. It has been determined that the use of glasspaper or cloth for the base sheets and the cover sheets provides a particularly eicient heater, as'glass has an extremely high coeiiicient of radiation, and thus ythe entire surface of the heating panel 54 will serve as a radiation area, though any other suitable material may be used.

ln Figures 14 and l5 there is illustratedyet another modification of this invention, which is particularly suitable for use in very high temperature work such as in a cooking or grilling plate designed tooperate at a temperature of approximately l300y to 1600 F. '-B'ase ,sheet 60 is formed of la high temperature resistance material such as an asbestos cloth or board, or other suitable nonconductive material. Disposed upon base sheet 60 are a number of apertured beads 62 which are disposed to carry a wire resistance element in slightly spaced parallel relationship with the base sheet 60. A high temperature resistance grid or plate 64 is threaded through the apertures of the beads 60 and may be drawn taut so that there is no slackness in the wire or grid. A plate of heavy Vicor glass 66 may be disposed in parallel relationship with the base sheet 60 `and the wire grid 64, :and is spaced a short distance from the wires. The heavy heat resistant glass will allow the radiant infra-red rays to pass therethrough, and forms a direct conta-ct element suitable for use as a hot plate or a stove.

In Figure 16 there is illustrated a relay circuit particularly adapted for use with heating and cooking elements etc., in circumstances where it is particularly desirable that the entire heating element be promptly raised to its final operating temperature. The heating element generally indicated at 68 is provided with a first power lead 70 land a second power lead 72 engaged with its respective ends. A third power lead is engaged with the resistance element 68 at a point intermediate its ends, and this lead will operate to short circuit the first lead when thermal operated relay 74 is closed. This relay, which may contain a well known bimetallic element, remains closed at normal or room temperatures and will thus be operatively interposed in the circuit when the heating element is first energized. However, as the heating element, or at least that portion of the element between lead 72 and lead 76, is energized, the resulting heat will cause the thermal operated relay to open, breaking the short circuit. The effect of this arrangement is that a rst portion, having a relatively low total resistance, of the heating element will be rapidly brought to its operating temperature, before the thermal operated relay opens. The opening of the relay will place the remaining portion of the resistance path in the circuit. The ow of current through this remaining portion of the resistance path, that is, between 70 and 76, will rapidly raise its temperature to a point where the ent-ire circuit has its usual operating temperature.

While wires of any of a large number of materials may be used in the various illustrations of the invention hereinbefore discussed, it has frequently been found desirable to use a wire of aluminum or other material having a high temperature-resistance coeicient. Ordinarily, such wires have been considered unsuitable for installation in heating appliances for domestic use. As electrical heating units are rated by Underwriters Laboratories in terms of initial wattage output when cold, and as such heaters are frequently used for protracted periods, it will be readily seen that the full or rated output is achieved during a very small fraction of the total time in which a particular heating unit is in use. Therefore, the heating potential, or the total capacity to produce the desired quantums of heat, is being wasted during a major portion of a given normal operating period.

It is within the contemplation of this invention to provide means which will eliminate this useless waste of the full heating potential of the elements. This end is achieved by providing the circuit with `a thermal operated relay interposed in a shunt which short circuits a portion of the resistance path of the element. For example, the cold or initial current of a typical aluminum grid element of 1000 watts capacity at 118 volts is 12 amperes producing 1418 watts. For a 1500 watt unit the cold or initial amperage is in the neighborhood of 18 amperes with an output of 2127 watts. Thus, the input watt-age when the unit is cold is much too high and will not meet the rigid requirements of the various electrical Underwriters Laboratories, which demand that a heater be designed in such a manner that it will not blow or burn out a l5 ampere fuse on a l 18 volt circuit.

It is therefore proposed to add an additional element or resistance 169, as in the heating circuit illustrated in Figure 17. The heater is Iarranged so that the current at the terminals normally flows through thermaloperated switch 174, joins the main resistance unit 168 at 176 and then ows from the element through lead 172 to terminal 162. The thermal-operated switch 174 is bypassed by a high resistance element 169 which may be either a separate resistance unit or a mere continuation of the main resistance unit 168. If the heating circuit is energized when cold, the thermal-operated switch 174 is open and the entire current flows through elements 169 and 168. As this circuit becomes warm, the thermaloperated switch will close, forming `a low resistance shunt around element 169 so that the major portion of the current will ow through the switch 174iand the main heating element 168. It will be readily seen that this arrangement will lower the resistance and increase the amperage ow to a level approximating that of the entire unit when cold.

This arrangement of the circuit allows a heating unit rated at 1500 watts to approximate this output during the entire period of operation and thus the wastage of the heating potential is eliminated. The wattage will sini-z momentarily when theelements 169 and 16S heat up, but when the thermal-operated relay closes, the resistance is immediately lowered sufiiciently to bring the wattage back to the desired level, that is, 1500 watts. It is noted that this 'arrangement is exactly the opposite of that shown in Figure 16 where the very high heat response is the performance factor desired.

lHaving described only a typical preferred form land application of the invention, it is not to be limited or restricted to specific details herein set forth, but I wish to reserve to myself any Vari-ations or modifications that may appear to those skilled in the art and falling within the scope of the following claims.

I claim:

l. An electrical heating unit comprising a base sheet of non-conducting material, a cover sheet of non-conducting material disposed on one side of said base sheet, `a wire resistance element disposed between said base sheet and said cover sheet and sewn to one of said sheets, a heat reflecting sheet disposed on the second side of said base sheet, and a mass of cured resinous material disposed between said base and cover -sheets and about said element, adhesively securing each one to the other.

2. An electrical heating unit -comprising -a flexible base sheet of non-conducting material, a exible cover sheet of non-conducting material disposed on one side of said base sheet, a Wire resistance element disposed on the rst side of said base sheet, said wire being periodically sewn through said base sheet, a heat reflecting sheet disposed on the second side of said base sheet and a mass of cured resinous material disposed between said base and cover sheets and yabout said element, adhesively securing each one to the other.

3. An electrical heating unit comprising a base sheet of flexible non-conducting material, a cover sheet of flexible non-conducting material disposed on la first side of said base sheet, a wire resistance element extending along said first side of said base sheet and being stitched through said base sheet, a non-conducting filament extending along the second side of said base sheet, said wire being stitched around said filament, said filament acting as an underthread, a heat reflecting sheet disposed on the -second side of said base sheet and a mass of cured resinous material disposed between said base and cover sheets and about said element adhesively securing each one rto the other.

4. An electrical heating unit comprising a base sheet of exible glass paper, a cover sheet of exible glass paper `disposed on one side of said base sheet, a wire resistance element extending along a first side of said base sheet and being stitched through said base sheet, a nonconducting filament on said second side of said base sheet, said wire 7 being stitched around, said4 lament, Vsaidglament acting as an underthread, a heat reflecting sheet disposed on the second side of said base sheet,.a mass of cured resinous material disposed between said sheets and about said element, adhesively securing each one to the "other,

5. In the apparatus dened in claim `4, a flexible glass sheet disposed between said base sheet and 4said heat reflecting sheet.

6. An electrical heating unit comprising a base sheet of non-conducting material, :a cover sheet yof non-conducting material d1sposed on one side of said base sheet, a wire resistance heating element including terminal means for connection to a source of electrical'power disposed between said base sheet and said cover Vsheet and sewn to one of said sheets, a heat Vreflecting sheet disposed on the second 4side of sai-d base sheet, ,a shunting circuit by-passing a portion of said heating element, said vshunt-ing circuit comprising a temperature responsive circuit opening and closing device, said device beingin heat exchanging relationship with the remaining portion of said heating element, the arrangement being such that said device opens upon an increase of the temperature of said element s'o that initially the main portion of the current ilows vthrough said remaining portions to heat said remaining portions rapidly.

7. A method or" forming electrical heating units comprising backing a ilexible sheet of non-conducting material with a heat reiiecting sheet, sewing a wire electrical resistance element to the opposite side of said base sheet, covering said element and said base sheet with a sheet of non-conductive material, dipping Asaid sheets and ,said element into a resinous bath, and curing said assembly.

8. A method of forming electrical heating units comprising backing a flexible base sheet ofvn'onconducting `material with a heat reflecting sheet, sewing a wire electrical resistance element to the opposite side ofA said base sheet, covering said element and` said base sheet with a. sheet `of non-conductive material, dipping said sheets and said element into a silicone varnish bath, andcuring said assembly. A .Y

9. A method of forming an electrical heating `unit comprising backinga exible glass basesheet with a heat reflecting sheet, sewing a wire electrical element through said flexible glass base sheet, covering Isaid base sheet and said element with `a sheet of glass paper, impregnating said sheets with a resinous material, polymerizing said material, and molding said assembly. v v Y l0. An electrical heating unit comprising a base sheet -otexible glass paper, a cover sheet of Vliexible 'glass paper disposed .on one side Vof said base sheet, awire resistance element extending along arst sideA ofV said base sheet and being stitched through said base sheet, a nonconducting lament on said second side of said base sheet, said wire vbeing stitchedaround said lament, said lament acting as an underthread, a heat reecting sheet disposed on the second side of said base sheet, a mass of cured resinous material disposed between said base and lcover sheets and about lsaid element, adhesively securing each one to the other, terminal means for connecting said wire resistance element with a source of electrical power,l heat responsive relay means disposed in the circuit shunt ing a rst portion of said resistance element and connected with said terminal means, said relay meansbeing arranged to open when heated by a second remainirigportion of said resistance element, the arrangement being such that saidfirst portion of said resistance element is by-passed when the element is cold, and said shunt is opened when said second portion heats said relay means.

ll. An electrical heating unit comprising a base sheet of `flexible glass paper, a cover sheet of iiexible glass paper, disposed on one side of said base sheet, a resistance heating element, a second resistance element, both of said resistance elements extending along a .rst -side of said base sheet and being stitched through said base sheet, a non-conducting filament on said second side of said base sheet, said non-conducting filament acting as an underthread for the stitching of said resistance elements, a heat reflecting sheet disposed over said lament on the second side of said base sheet, a mass of cured resinous material diposed between said'base and cover sheets and about said resistance elements, adhesively securing each one to the other terminal meansv for connecting said resistance elements with a source of electrical power, heat responsive relay Imeans disposed lin a circuit shunting said second resistance element `and connected with said terminal means, said relay means being arranged to close when warmedy by said heating element, the arrangement being such that said second resistance element is by-passed when the heating element is warm and said shunt is open when said heating element is cold.

References Cited in the le of this patent UNITED STATES PATENTS 1,142,393 Bloomer June 8, 1915 1,696,684 Knopp Dec. 25, 1,928 2,100,326 Getchell Nov. 30, 1937 2,467,349 V-an Daam Apr. l2, 1949 2,559,077 Johnson et al. July 3, 1951 2,617,916 Neidnig Nov. 11, 1952 2,674,683 Rand Apr. 6, 1954 2,719,907 Combs Oct. 4, 1955 FOREIGN PATENTS 604,766 Great Britain July 9, 1948 

